QUANTUM EFFICIENCY OF PHOTOSYSTEM-II IN RELATION TO ENERGY-DEPENDENT QUENCHING OF CHLOROPHYLL FLUORESCENCE
QUANTUM EFFICIENCY OF PHOTOSYSTEM-II IN RELATION TO ENERGY-DEPENDENT QUENCHING OF CHLOROPHYLL FLUORESCENCE
复制标题
DOI：
10.1016/0005-2728(87)90190-3
复制
发表时间：
1987-11-19
期刊：
影响因子：
--
通讯作者：
BERRY, JA
中科院分区：
文献类型：
--
作者：
WEIS, E;BERRY, JA
在细胞间CO2浓度恒定的条件下，通过改变入射光通量，可以改变完整向日葵叶片中光依赖反应和电子消耗反应之间的平衡。荧光猝灭的测量进行了比较，在一些稳态条件下的全链电子传递的速率和表观量子产率的测量。稳态量子产率随着光强度的增加而下降，在最高强度处下降到约100%。在弱光下观察到的最大值的40%。光化学猝灭的系数qQ在低光下接近1，在最高光下仅下降至0.7，表明还原电子载流子的积累几乎没有反馈。另一方面，随着量子产率的下降，qE（“能量”依赖性淬灭的系数）有很大的增加。我们发现，稳态量子产率Φs的这些变化可以通过经验方程Φs=qQ（0.32 − 0.17qE）与荧光猝灭的变化相关，该方程解释了光饱和或CO2浓度变化导致的Φ s变化。我们提出了一个假设，即光系统（PS）II中心可能被转换到一个改变的状态（可能是由叶绿体ΔpH值介导的），它具有非常小的可变荧光和降低的光化学产额。我们开发了一个动力学解释PS II的改变形式的属性，我们提出，这种机制（表示由QE）的功能与减少QA（表示由qQ）的积累一起调节PS II的净光化学速率时-随着光照的增加或减少CO2-净光化学的潜在速率超过碳代谢。后一种机制显然允许PS II的下调发生而没有强的积累减少QA，除了在瞬态或在最极端的条件下。
The balance between light-dependent reactions and electron-consuming reactions in intact sunflower leaves was varied by changing the incident light-flux at constant intercellular CO2concentration. Measurements of fluorescence quenching were compared to measurements of the rate and apparent quantum yield of whole-chain electron transport at a number of steady-state conditions. The steady-state quantum yield declined with increasing light intensity, falling at the highest intensity to approx. 40% of the maximum value observed in low light. The coefficient for photochemical quenching,qQ, was near 1 in low light and only declined to 0.7 at the highest light, indicating that there was very little feedback from accumulation of reduced electron carriers. On the other hand, there was a large increase inqE, the coefficient for ‘energy’-dependent quenching, as the quantum yield fell. We found that these changes in the steady-state quantum yield,Φs, could be related to the changes in fluorescence quenching by an empirical equation,Φs=qQ(0.32 − 0.17qE) which accounted for variation inΦsresulting from light saturation or changes in CO2concentration. We develop a hypothesis that Photosystem (PS) II centers may be converted to an altered state (possibly mediated by the chloroplast ΔpH) which has very little variable fluorescence and a lowered photochemical yield. We develop a kinetic explanation for the properties of the altered form of PS II, and we propose that this mechanism (indicated byqE) functions together with the accumulation of reduced QA(indicated byqQ) to regulate the rate of net photochemistry by PS II when — with increasing light or decreasing CO2— the potential rate of net photochemistry exceeds that for carbon metabolism. The latter mechanism apparently permits down-regulation of PS II to occur without strong accumulation of reduced QA, except during transients or under the most extreme conditions.